Vacuum cleaners which utilise cyclonic separators are well known. Examples of such vacuum cleaners are shown in EP 0 042 723, EP 1 370 173 and EP 1 268 076. In general, an airflow in which dirt and dust is entrained enters a first cyclonic separator via a tangential inlet which causes the airflow to follow a spiral or helical path within the first cyclonic separator so that the dirt and dust is separated from the airflow. Relatively clean air passes out of the first cyclonic separator while the separated dirt and dust is collected therein. In some applications, and as described in EP 0 042 723, the airflow is then passed to a second cyclonic separator which is capable of separating finer dirt and dust than the first cyclonic separator.
However, a common problem is that larger particles of dirt and dust (for example, fluff or hair) not separated by the first cyclonic separator are able to pass into the second cyclonic separator, resulting in potential blockages and a loss of separation efficiency. Therefore, it has been found useful to position a barrier member, known as a shroud, in the airflow path between the first cyclonic separator and the second cyclonic separator. An example of a typical shroud is shown in EP 0 800 360.
A shroud typically includes a wall having a large number of through-holes which communicate on their upstream side with the first cyclonic separator. The through-holes of the shroud thus form an outlet from the first cyclonic separator. In use, the through-holes of the shroud prevent larger particles of dirt and dust from passing therethrough. However, smaller particles of dirt and dust not separated by the first cyclonic separator pass through the through-holes in the shroud and into a passageway leading to the inlet to the second cyclonic separator.
EP 1 377 196 describes a passageway in the form of an annular passageway located downstream of a shroud. Baffles are located in the annular passageway remote from the shroud to divide the airflow between a plurality of cyclones which form the second cyclonic separator.
An alternative passageway arrangement is shown in EP 1 786 568, which discloses a shroud for a vacuum cleaner having two cyclonic separators. The shroud forms an outlet from the first cyclonic separator, and a passageway is located downstream of the shroud. A plurality of baffles is located on the inner surface of the shroud in the passageway. The passageway forms a communication path between the shroud and the inlets to a plurality of cyclones forming part of a second cyclonic separator. The bodies of the cyclones extend through the passageway and into a collector located below the passageway. Such an arrangement is well known for cyclonic separating apparatus having two cyclonic separators.
However some, more recent, vacuum cleaners include cyclonic separating apparatus which has more than two cyclonic separators or separation stages. Cyclonic separating apparatus including three cyclonic separators is disclosed in WO 2006/125944. In the arrangement described therein, three collectors for dirt and dust are provided—one for each cyclonic separator.
In such an arrangement, the increased number of cyclonic separators and collectors reduce the space available for the passageway downstream of the shroud. To provide sufficient space to accommodate the passageway, the diameter of the shroud may be increased, leading to an undesirable increase in the overall size of the cyclonic separating apparatus.